jojobajim

Confounded by an OS 70 surpass II with pump! I have run OS four strokes since before they were surpass's and love them, but! This 70 with pump has me buffaloed. In the beginning it would not even run, but after finally calling the factory rep/(don't remember who) we checked the valve clearances and there were minimal adjustments to be made ( slightly tight but near tolerance) Changing fuel to YS 20/20 got the engine to run, but the runs are not consistent with high end changing from rich to lean from run to run and the idle adjustment just all over the place. Multiple glow plug changes had no effect on the erratic behavior. I suspect without any real reason that the pump pressure may be varying from run to run, but with a pressurized tank I doubt this would be a factor. There are no leaks in the system that I can find and have even replumbed the tank to check for changes to no avail. All fuel is double filtered, in to the tank and to the engine. Honestly, I now wish I had forgone the pump since I never needed one in the past! and would trade back at the drop of a hat! This is rather a hail Mary pass for help. PS, although age and experience don't equate to knowledge, I have been in the hobby for over 40 years! (maybe I've forgotten something relevant) Thanks for any help available.

Bax

My Feedback: (11)

First off, how are you setting the engine. To get it properly-set, you really need to use a tach. Lean the engine to peak RPM and then leave it there. Do not lean it and then richen it.

Usually erratic RPM on pumped engines is caused by net leaning them enough. You want to lean your engine as far as possible without detonation or RPM drop, and leave it there.

If the engine still has problems, then it may need to come into the service department.

Capt. Crackup

My Feedback: (1)

Bill, I read this post with interest. I am fairly new to 4-strokes..... have been running them now for about a year maybe 16 monthish. I have a surpass 52 and surpass 70...I love them. Fortunately my engines run great but I was wondering if the above proceedure applies to the non pumped engines as well?
Thanks Skip D.


Bax,,Disregard. I found the answer in a 70 surpass surging. Thanks

jojobajim

Bill, Thanks for the response. I have been backing off just a hair from maximum rpm and will try not to and see if that smooths things out. I was afraid of being too lean. I'll get back on this when I have tried the settings. Cold and windy in Montana this time of year, but we're going to try skiis this afternoon on a Twist.

jojobajim

Bill, Too cold to test! Will continue on this. Thanks again for your patience and assistance. Jim

jojobajim

Bill, Got warm enough to try the engine again. First, I mis identified the engine. It's the FS 70 Ultimate pumped engine, blue head, not the surpass as I said before.sorry. I tried the leaning technique you mentioned with a tach and the high end was improved, but the idle was still strange. One time it would be pretty good with a normal transition to high, then the next time, with no changes, it would appear to load up and then die. I tried to gradually turn the idle screw in with no affect until it just died. Opened it up and ran fine for a partial flight (several touch and go's) and then repeated the loading problem. I am out of ideas and really unhappy with the expensive engine. Would prefer to have the old tried and true surpass option of yesterday. What would you suggest?
regards, Jim

Bax

My Feedback: (11)

The O.S. FS-70 Ultimate has had difficulties off and on. It varies from engine to engine. Please send it to us and we'll see what we can do to help you.


Skip:

The leaning instructions above apply only to the pumped engine.

jojobajim

Thanks for the support. The engine is with UPS and should be with you by Thursday. I saw my son's apology and I include mine. Frustration is a terrible thing! smile! tracking number 1z1r9a440330963094

jojobajim

Gentlemen, I want to thank you for the timely and fair resolution of this problem. You can know that I will pass on the good report of your service. I am impressed with your entire service group.

respectfully yours, Jim Hochhalter

Bax

My Feedback: (11)

We're glad something could be worked out.

jojobajim

Received the replacement engine today. Thanks again for the kind service. Don't you know that winter returned last night and now it will be a while returning to the flight line, even with skiis. Oh well...Time to build.
sincerely, Jim Hochhalter